The present invention relates to a metal detection system and especially to a spot indicating metal detector having rotating metal detectors mounted on a remotely controlled platform.
A metal detector is a device which responds to the presence of metal. It may consist of an oscillator producing an alternating current that passes through a detector coil producing an alternating magnetic field. When metal is brought close to the coil, a current is induced in the metal and produces an alternating magnetic field. A second coil is used to measure the changes in the magnetic field due to the metallic object detected. A metal detector can be made to discriminate between metals by the use of an induction balancing system in which two coils are electrically balanced. Different metals have different phase responses when exposed to alternating current so that the metal detector can selectively recognize different metals.
Metal detectors typically use a beat frequency oscillator or an induction balancing system but also sometimes use a pulse induction detection. The pulse induction detector fires a high voltage pulse into the ground and measures the decay of the pulse for the voltage to drop to zero.
Prior art metal detectors used by amateurs and treasure hunters are commonly hand-held metal detectors mounted on an elongated arm having a search coil head on one end with an electronic power supply and operating controls at the handle end. Manually supported metal detectors have become common for use by treasure hunters and hobbyists in the search for coins and metal objects buried in the ground. The metal detector is held by the user in one hand without any supporting device to carry part of the weight. A detector arm is then extended at an angle to position the detector coil a short distance above the ground and moved back and forth in a pattern over the surface of the earth. The detector coil picks up a signal when a metal object is located beneath the coil head.
The De Vries U.S. Pat. No. 4,797,618 provides a wheeled carrier for a metal detector to facilitate the use of the metal detector being moved across the earth. There has also been a number of suggestions for placing a metal detector on a remote controlled platform, such as can be seen in the Butler et al. U.S. Pat. No. 5,307,272 for a minefield reconnaissance and detector system. Mine detection systems have also been devised having remotely controlled sensors, such as seen in the Das et al. U.S. Pat. No. 6,333,631 for a cantilevered manipulator for autonomous non-contact scanning of natural surfaces for the deployment of landmine detectors. The Straus U.S. Pat. No. 5,869,967 is for a device for the detection of objects, especially explosive objects, lying in the earth.
It has been recently suggested to have a remote controlled metal detector using a remotely controlled buggy having a metal detector mounted thereon which can send an audible beep when metal is detected by a metal detector on the remotely controlled buggy.
In the present invention, a spot indicating metal detector rides on a motorized platform with a rotating frame having a plurality of metal detectors mounted thereon. The metal detector scans the earth below and actuates a spray system upon the detection of metal and sprays a marker fluid onto the earth to mark the actual spot where metal is detected. The motorized platform may be remotely controlled.